I had a 4.7" HTC One (M7). I've had a few BlackBerries. I have a house full of Macs, iMac, iPod Nanos, Apple TV, iPads, ect. But never an iPhone. I always thought 4.7" was the perfect size. The 6+ came out, and I was wrong. When I finally got the wife to agree to a smart phone, she took my M7 and I went to a Q10. She complained that the phone was too big. She now has an iPhone 6, and she no longer complains about the phone being too big.
Will Apple go bigger than 5.5" ? Who knows. Maybe, if the demand is there. One thing I won't do is swear off a phone bigger than 5.5". I am glad I went with the plus and not the plain old six. 5.5" screen is plenty, for now.
Funny thing, now that I have the 6 and 6 Plus, when I need to use my wife's 5 or the kids 5c's they feel really small
I have the plus, I feel the same way when I pick up the wife's 6.